DOUBLER
OPERATO'R'S
MANUAL
Copyright 1980 Micromatiorl', Inc
1620 Montgomery San Francisco, CA 94111 All rights reserved worldwide.
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Micromation Incorporated makes no representations or warranties with respect to the contents of this document and specifically disclaims any implied warranties of merchantibility or fitness for any particular purpose. Further, Micromation reserves the right to revise this publication and to make changes as necessary in the content hereof without obligation of Micromation to notify any person or organization of such revision or changes.
DOUBLER - 4.80
Section 1 1 1-1 1-2 1-3 1-4 2 2-1 2-2 3 3-1 3-2 3-3 3-4 3-5 3-6 4 4-1 4-2 4-3 4-4 4-5 5 Section 2:
6 6-1 6-2 7 7-1 7-2 7-3 8 8-1 8-2 8-3 8-4 8-5
9 9-1 9-2
MICROMATION DOUBLER
FLOPPY DISK CONTROLLER
TABLE OF CONTENTS
Introduction
Hardware Interface Bus Interface
Disk Interface
Special Interface Requirements
1 1 1 2 2
Controller Options 3
Necessary Hardware 4
Console Device Connection 5
DOUBLER Installation 5
Preparation 5
Baud Rate Selection 6
Jumper Options 6
Board Insertion 6
Cable Installation 6
Booting the Systems 7
Use Of CP/M with the DOUBLER 10 Diskette Handling and File Maintenance 10
Standard CP/M Utilities 11
Micromatin Utilities 12
Other Files 15
The Micromation BIOS 16
CP/M Interversion Compatibility 17 Theory of operation
In trod uc tion
Disk system operation Disk read/write
The S-100 bus interface The control bus
The data bus The address bus
Address bus decoding The address decoder PROM The C2-PROM
The scratch pad RAM
The read and write control The UART
Disk drive interface
The phase lock oscillator The byte sync counter
18 18 19 20 20 21 21 21 21 21 22 22 23 23 24 25
9-3 Wait states (XRDY or PRDY) 9-4 The cyclic redundancy check
9-5 Encoding and write precompnsation 10 The RS232 serial interface
11 Power on Jump 12 Power supply
Appendix A: The Disk Format Appendix B: C2-PROM listing Appendix C:
Changing Operating System Characteristics C-l Changing the System Size
C-2 Changing the IOBYTE default and Step C-3 BIOS and BOOT Alteration
Appendix D: Schematic diagrams
26 26 27 27 28 28 29 31
46 46 Time 48 52
DOUBLER
OPERATOR'S MANUAL
1 INTRODUCTION
The DOUBLER is a high performance floppy disk controller designed for the 8-100 bus. Its proper installation in an 8-100 system will provide reliable operation at the highest speed and capacity currently possible with floppy disk technology. The controller is designed to interface directly with CP/M*, an operating system which has file management facilities and software utilities comparable to the most advanced computer systems. To ensure full utilization, the user of a DOUBLER system should be acquainted with the options available and its general method of operation.
1-1 HARDWARE INTERFACE
The DOUBLER will provide all the functions required for single or double density floppy diskette operation for 8-100 bus computer.
It uses the IBM 3740 format for single density recording {26 sectors of 128 bytes each}. In double density, the DOUBLER uses a version of the IBM 2D format modified for 52 sectors of 128 bytes
to maintain compatability with CP/M. The board uses the system processo r to con trol d rive func tions. The transfe r 0 f disk data is done under program control in order to assure reliable operation. The board requires two thousand {2K} bytes of system address space: lK is used by the 2708 EPROM and the remainder is used for an on-board RAM scratchpad and memory-mapped I/O locations. All I/O operations are handled through memory locations in the board's address space, so no I/O mapped ports are required.
1-2 BUS INTERFACE
Detailed interface information is available by referring to the schematics included in appendix D. Address decoding for the board is accomplished by a 256 x 4 bipolar PROM. When the proper address appears on the bus, the appropriate strobes are generated. Further decoding of the strobes for input and output functions provides strobes for individual operations. A power-on- jump is accomplished by disabling the memory at location 0 after a reset with the phantom line. The on-board EPROM is then enabled and a jump instruction to the bootstrap routine is sent to the processor. The board synchr.onizes the disk drive with the processor by holding the system ready line low until the disk interface is ready for another byte of data. Circuitry on the board prevents the ready line from remaining low for a period of time longer than that required to transfer eight bytes of data from the disk.
* CP/M is a registered trademark of Digital Research, Inc.
1-3 DISK INTERFACE
Software routines in the EPROM direct the generation of signals necessary to control the disk drives. The output signals are latched in a latch/driver. The input signals are read by the.
system through an input port. Circuitry is included to cause the drive head to unload if there has been no disk access during eight revolutions of the diskette.
When reading data from the disk drive, the controller derives its data clock from the data on the diskette by generating a signal called PLO. This signal represents a phase lock oscillator and maintains synchronization with the disk data without being sensitive to the shift of individual bits. During write operations, the PLO is derived from the crystal clock and controls the data pulses written to the disk. During write operations in double density, the PLO signal is shifted under special conditions to cause the data written to the diskette to be "pre-compensated." Special circuitry prevents inadvertent writing to the diskette by unintentional memory accesses.
Error checking of all disk operations is done by computation of the sector's CRC. The CRC checking is done in hardware, so the system is capable of reading or writing consecutive sectors.
1-4 SPECIAL INTERFACE REQUIREMENTS
The DOUBLER and Micromation CP/M are currently configured to interface Shugart single-sided or Remex or YE Data double-sided drives. In addition, the controller can be factory configured for PerSci model 277 drives. Call Micromation for other drive types supported. This is especially important if you are thinking of upgrading your system with the DOUBLER.
FOUR-DRIVE SYSTEMS: The DOUBLER and associated CP/M are designed to support from I - 4 drives without modification. Each drive must be from the same manufacturer and be of the same type
(single- or double-sided) , however.
DRIVES REQUIRING ABOVE TRACK 43 CONTROL: Some floppy disk drives require a signal to indicate that the head is positioned above track 43. This signal is available from the controller and is generally connected to the disk interface connector on pin 8.
Some drives require this signal on a different line, however, and the user should verify the operation with the particular drive being used.
2 CONTROLLER OPTIONS
The DOUBLER has several options to make i t the most powerful controller available. Their functions and factory settings are reviewed below. Note that all the jumpers described below except the WAIT jumper are in the form of traces. To disable the function, the trace must be cut. (A header can be installed to facilitate re-enabling the jumper.)
POJ: Connection of this jumper (located near device 7C) enables the power-on-jump function of the DOUBLER. This feature operates by driving the "phantom" line on pin 67 of the S-100 bus low after a reset. This should disable the output buffers of the low memory. Check with your system technical manual of the memory used in this area to ensure that it supports the "phantom" line.
If i t does not, the controller's power-on-jump cannot be used, and another method of transferring control of the processor to the bootstrap routine must be used. When enabled, the DOUBLER's power-on-jump circuitry causes the system to jump to the cold bootstrap routine located in PROM on the controller board. The DOUBLER is shipped with the power-on-jump enabled. To disable it, remove the jumper between the pads marked "POJ".
PHANTOM: This jumper (located near device D4) connects the line used to disable RAM while the DOUBLER executes a power-on-jump.
It ordinarily is connected to pin 67 of the S-100 bus, but can be jumpered to any other pin which the user's system supports. The reference manuals of the system should be checked to determine whether any other boards use pin 67. A few processor boards use this line to output the refresh signal from Z-80 processors. This should be disabled or disconnected if the DOUBLER's power-on-jump circuitry is utilized.
XRDY & PRDY: The DOUBLER uses the ready line to synchronize the processor wi th disk data. Di f ferent systems, depend ing on front panel or dynamic memory design, require that peripherals use XRDY and PRDY on the S-100 bus. The DOUBLER can use either line. It is shipped with jumpers (located near device D4) enabled to use both XRDY and PRDY. If either adversely affects the system operation, it may be disconnected by cutting the trace where marked.
WRITE: In order to prevent unintentional writing on a diskette, a write enable jumper (located near device 7A) is installed. This jumper must be in place in order to write on a diskette. If the floppy disk drives that are being used do not support write protect (all Micromation systems do), it is recommended that this jumper be removed until the system h a s b e e n 0 per ate d successfully and whenever the user wants to ensure that a diskette is not written upon.
HEAD: Standard Shugart-type drives support a signal named HEAD LOAD on the disk interface cable. This signal is used to load and unload the head of a selected drive, so the drive select buffers may remain enabled. Other drives, such as PerSci, use the drive
select lines to unload the head. With these drives, the drive select lines must be disabled in order to unload the head. The DOUBLER unloads the head of a selected drive if a read or write operation has not occurred during the past eight revolutions of the diskette. Ordinarily this is done by disabling the HEAD LOAD line. If the controller is used with PerSci-type drives, the HEAD jumper (located near device l0A) must be switched to its alternate position. This will disable the drive select buffers to unload the head.
WAIT: To facilitate operations withZ-S0 processors, a WAIT jumper (in the form of a header located near device D5) is available. This causes a wait state to be added only when the board is addressed. This is necessary to enable the on-board 27~S
EPROM to be accessed and to allow time for the disk control circuitry to be properly set-up. This wait state will not affect overall system speed since during disk operations the speed of the system is controlled by the transfer speed of the disk data.
The WAIT jumper must be connected when the DOUBLER is used wi th any S080 system or when the DOUBLER is installed in a Z-S0 based system operating at 4 MHz. If a 2 MHz Z-S0 processor is used, WAIT should not be connected. The DOUBLER is shipped with the WAIT jumper installed. It should be removed only when operating with a 2 MHz Z-S0 processor.
2-1 NECESSARY HARDWARE
Micromation DOUBLER floppy disk systems are designed to operate with all standard S-100 systems with 2 to 4 MHz S0S0 or Z-S0 processors. Since the controller performs a power-on-jump, it can be used in systems with or without a front panel. The operating system requires at least 16K bytes of RAM contiguously addressed in the lowest addresses of memory. The controller occupies 2K bytes of memory generally located at the top of the addressable memory range, from FS00 to FFFF. The user should ensure that there are no memory address conflicts with other boards in the system. The DOUBLER may be addressed at locations C000, D000' E000 or F000 by obtaining special PROMs from Micromation.
2-2 CONSOLE DEVICE CONNECTION
A console device is necessary to communicate with the system. The DOUBLER includes a full function UART to communicate with RS-232 type terminals. The software provided with the system is programmed to use the UART on the controller to communciate wi th the console dev ice. Optional so ftware drivers for the Processor Technology SOL and NorthStar Horizon are also available from Micromation.
NOTE: The DOUBLER derives the clock input for the UART from the CLOCK signal on pin 49 of the S-1012l bus. This must have a 2 MHz·
frequency for the UART to function. Check your system manual to
ensure that pin 49 has a 2 MHz clock on it. If your system does not, install the necessary jumpers to provide the requisite sig nal •
CONSOLE DEVICE INSTALLATION: Installation of the hardware is straightforward. To initially bring up the system, the minimum amount of hardware should be used. This is just the disk controller, processor board, and, at least, 16K to 32K of memory
in the lowest address of RAM. An RS-232 terminal should then be connected to the controller board. The controller has a 10 pin socket header with cable on the right side of the board. The pins are labelled to indicate their RS-232 function. The following table may be used to connect an RS-232 terminal. A ten foot cable with RS-232 connector is available from Micromation. Most RS-232 terminals require only three signals (ground, transmitter data, and receiver data) to be connected. The other signals are for terminals which require handshake operation.
DOUBLER SIGNAL TERMINAL
HEADER PIN NAME RS-232 PIN
2 GND 7
1 TxD 3
3 RTS 20
5 DSR 4
9 RxD 2
GND The ground signal sets a common reference between the output and input devices.
TxD Transmitter Data is that data output from the CPU to the te rminal.
RTS Request to Send informs the terminal that the CPU has some data to output. This signal is used only when handshaking is necessary.
DSR Data Set Ready active indicates that the terminal is ready to receive data. The terminal sends a signal called Data Terminal Ready (DTR) to this pin. The processor checks this bit before i t sends the character. This, also, is only necessary with terminals that require handshaking.
RxD Receiver Data is that data output from the terminal to the processo r •
3 DOUBLER INSTALLATION 3-1 PREPARATION
Before installing the DOUBLER in your system, clean off the S-100 edge connector fingers wi th alcohol on a cotton swab. This will remove any oxidation or finger prints. Do not use any other cleaning agents (e.g., a solvent, emory cloth, ink eraser, etc.), as these may damage the connector fingers.
3-2 BAUD RATE SELECTION
Any baud rate from 110 to 9600 can be selected with the prop~r
jumper. The baud rate selection jumpers are in the upper right side of the DOUBLER, just to the right of the RS-232 connector.
Do not confuse the two. The baud rate jumpers are in ~he form of a l6-pin connector; the RS-232 connector has 10 pins.
The selectable baud rates are labelled on the board. The DOUBLER is shipped with a jumper setting the rate at 2400. Before installing the board, remove the jumper and place i t in the position that corresponds with the setting on your terminal.
Most terminals also feature a selectable baud rate. Ensure that the setting on the DOUBLER matches the setting on your terminal.
If you are in a quandary as to which setting to choose, 9600 BPS (bi ts pe r second) is a po pul ar rate.
3-3 JUMPER OPTIONS
Read the CONTROLLER OPTIONS section above and install or remove the appropriate jumpers for your system.
3-4 BOARD INSERTION
Turn off power to the computer and floppy drives.
Install the DOUBLER in a slot in the S-100 mother board. Place the controller as close to the processor card as possible.
Ensure that the card is pressed down into the edge connector all the way. Note that S-100 fingers are offset from the side preventing mis-orientation of the DOUBLER in the card cage.
3-5 CABLE INSTALLATION
Connect the 50 conductor ribbon cable from the floppy disk drives to the 50-pin connector on the DOUBLER. Pin 1, indicated by a red stripe on the edge of the cable, must be connected to header pin 1 on the left side (as viewed from the component side) of the board.
Connect the RS-232 terminal to the controller. Again, pin 1 of
the 10-pin cable attaches to the left side of the DOUBLER connector.
NOTE: Pin I of. this cable is typically indicated by a red stripe. If no such stripe is present on the cable, an arrow or indentation molded into the plastic cable connector also designates pin 1.
The figure below illustrates the top of the DOUBLER for use with cable installation and baud select
PIN 1
COMPONENT SIDE
1 - SER I AL CABLE FOR TERMINAL
BAUD RATE
DOUBLER CABLES AND BAUD SELECT
3-6 BOOTING THE SYSTEM
Before loading the operating system, read the CP/M Licensing Agreement and mail the registration card to Digital Research.
Only registered owners are entitled to updates.
Of course, you should become familiar with the CP/M operating system as well. Begin with the booklet An Introduction to CP/M Fe a t u res and Fa c iIi tie s • T his s h 0 u Id be f o 11 0 wed wit h C P /
M2.2
User's GufOe for CP/M 1.4 Owners fo r a discussion 0 f the updates from the previous version included in the new release. The remainder of the documents shipped with the O/S (operating system) can be read when the need arises.
NOTE: CP/M version 2.2 is being shipped at the time of this writing. As new revisions are distributed by Digital Research, Micromation makes the necessary modifications and ships them with the units. To accommodate this flux, 2.x will be used as a descriptor in the examples that follow.
To boot the system,
Turn on the power to the floppy drives and the terminal.
Turn on the power to the computer and press the reset button.
Ensure that the distribution diskette from Micromation is write protected. For systems with drives that check the write protect notch of the diskette, leave the notch exposed. (The figure below shows the location of the notch.) If your drives do not support this feature, remove the WRITE GATE jumper described above from the DOUBLER.
Insert the distribution disk in drive A with the label facing up (see the illustration below) and close the door. In Micromation systems, drive A is the bottom drive where the drives are mounted vertically; the left drive in our systems
with horizontal mounting.
DRIVE A DRIVE B
~
DO~
WRITE PROTECT NOTCH
. ~}O 0
- - 0
D-C
LABEL FACING UP . DISKETTE ORIENTATION
(Horizonal Mounting)
If the computer has a RUN/STOP switch, hit RUN. If the DOUBLER's power-on-jump is not being utilized, use a front panel or moni tor to cause the system to execute the prog r-am at location F800 (or at the base address of the controller if it is located at a different location).
Drive A should home (go to track 0), step twice, and within two or three seconds display
62k CP/M - Micromation ver 2.x A>
where the first line is the sign-on message and "A>" is the CP/M prompt. "A" indicates the current drive.
To view the contents of the disk, type "DIR". This is the CP/M command to display the directory of the files on the diskette.
The system responds with the names of the files.
This is the sequence for booting the system. It is referred to as a cold boot and need only be performed when the system is first turned on. Subsequently, a control-C can be used to load the system when necessary. This is called a warm boot and is only mandatory when diskettes are changed. In the event of a program crash, a cold boot may be necessary to get out of the program and back to the operating system.
The following chapeter discusses the utilities (called transient commands in the CP/M documents) provided on the distribution diskette and provides some exercises to demonstrate their use. We strongly recommend that the' operator(s} perform(s} these exercises to get hands-on experience in the use of the computer system.
4 USE OF CP/M WITH THE DOUBLER
4-1 DISKETTE DANDLING AND FILE MAINTERAHCE
There are some precautions that should be observed to ensure that your files aren't inadvertently lost due to operator error or the slings and arrows of outrageous fortune.
I) Handle the diskettes wi th care. Keep your fingers away from the exposed areas on both sides of the disk. Store diskettes in the paper sleeve whenever they are not in the computer (dust accumulates, otherwise, and shortens the life of the read/write head on the floppy drive). Since diskettes are a mag netic med ia, be sure to keep them away from magnets. Yo u should also keep the diskette out of direct sunlight and away from extreme heat. Never remove the mylar disk from its protective paper enclosure nor abuse ,the disk by folding or bending it. When possible, write the label before applying it to the diskette. Subsequently, use only felt-tip pens for additional notes.
2) ALWAYS make a back-up of your data files. In many cases great time and effort is spent creating these files. It is much easier to make back-up copies on an on-going basis than to re-enter the whole thing over again. Make a back-up of any files changed every time they're changed. (After the program has terminated and the O/S prompt has re-appeared, of course .)
3) NEVER power down the disk drives during program execution nor with a disk in a drive and the door closed. Clear the drives of a-II diskettes before turning off the power to the drives (opening the drive door will do). Powering down during program execution will, at least, render the data files suspect or, worse, trash a couple of sectors rendering the whole file useless. Turning off power with a diskette in the drive (but not during program execution) may also trash a sector or two as the head responds to powering down.
4) Write protect your important diskettes. The little notch on the left side of the leading edge (see the figure above) causes write protect when exposed. Cover it with tape (or
the silver squares frequently provided with this type of diskette) and the diskette can be written on. The CP/M system disk provided wi th the DOUBLER has the notch exposed so the disk cannot be written on or formatted (erased).
If these precautions are observed, very few problems will arise and those that do can be easily repaired with the back-up disks.
4-2 STANDARD CP/M UTILITIES
These two utilities will be used frequently. Diskettes used for program execution {and development) should contain these programs for diskette monitoring (with STAT) and file back-up (with PIP).
STAT.COM: This utility is used primarily to indicate the status of the disk space. It can indicate, for instance, the amount of space remaining for file storage, how much space a certain file takes up, how much space a group of files takes up, etc. Slightly different invocations display or change the current logical assignments of the peripheral devices.
PIP.COM: PIP is short for Peripheral Interchange Program.
It is most frequently used to transfer files from one disk to another in multi-drive systems. It is also used to transfer files between devices (from disk to list device, from paper tape reader to disk, etc.).
The next three programs may be useful, depending upon the application of the your system.
ED.COM: This is the CP/M text editor for creating and altering files. Although ED can be used for word processing, it is not recommended. There are several word processing programs available that are much better suited to this application. Primarily, it is useful for creating and ed i t ing prog ram files.
SUBMIT.COM: A limited form of batch processing is available with SUBMIT. This is most useful when a sequence of transient commands is frequently performed. A source file containing these commands is created with the editor for subsequent execution{s). There is no limit to the number of times this file is SUBMITed.
XSUB.COM: XSUB enhances SUBMIT by allowing line input to programs in addition to CCP input. Refer to the CP/M 2.2 User's Guide for CP/M 1.4 Owners for a descriptio-n
Of
XSUB. - - - -
The following utilities are used to generate a new system and to transfer the system from one disk to another.
MOVCPM.COM: This utility is used to move the CP/M system from one location in memory to another. CP/M should be loaded into the uppermost part of memory allowed by the computer system unless a special application requires differently.
SYSGEN.COM: Primarily, this utility is useful for trans- ferring the system image between different density disks (single to double, double to single). Additionally,
SYSGEN is used when a new system image is created and recorded. An illustration of its primary use is given in DISKETTE PREPARATION below.
The next four utilities are pertinent to assembly language programming. Many end users will never need these programs.
ASM.COM: This is the CP/M 8"8" assembler. A program of commands from the 8"8" instruction set can be assembled rendering two files, x.HEX and x.PRN, where 'x' is name of the program file. The .PRN file contains the original program listing plus the machine code. The .HEX file contains only the 8"8" machine code in the Intel "hex"
format.
LOAD.COM: The LOAD command converts a .HEX file created by ASM to a. COM file (which indicates that i t contains machine executable code). Once an assembly language program has been LOADed, i t can be invoked by merely typing the file name when the CP/M prompt is displayed on the console. That is, the program has the status of a CP/M util i ty.
DUMP.COM: The DUMP program displays the contents of the designated file on the console device in hexadecimal form.
DDT.COM: DDT, which stands for Dynamic Debugging Tool, allows inter'active testing and debugging of programs. An assembly language program can be tested, altered, patched, executed and/or repaired "on the fly" under DDT.
4-3 MICROMATION UTILITIES
The utilities described below were developed by Micromation to reconc i1e CP/M wi th Micromat ion equipment and to make computer operation easier. Note that the following describes the utilities provided with the standard Micromation CP/M system.
FORMAT.COM: Before using them to store data, diskettes must be formatted. This procedure writes a code on the diskette identifying each track (77 concentric circles around the diskette) and sector (26 or 52, depending upon the density, sections within each track). Thus, each location on the diskette is uniquely identified and can be individually accessed. There are two formats for standard 8" diskettes: single and double density. The diskette shipped with the DOUBLER is recorded in single density and contains about 25" ki1obyte-s (25"K) of read/write space.
Diskettes with a double density format have about 5""K bytes of file space.
To format a diskette in drive B in double density enter:
FORMAT BD@
Where FORMAT indicates the program, B the drive containing the diskette and D the density.
To format a diskette in drive B in single density enter:
FORMAT BS@
Where S indicates single density.
The diskette in drive A can be formatted. However this will erase the diskette. Do not attempt to boot from the diskette in drive A after it has been formatted.
IMPORTANT: The format program should be used with care. When old diskettes that have information stored on them are formatted, all data is erased as part of the process. If a used diskette requires formatting (e.g., to make i t double density from single densi ty) be aware of this fact. There is no way to recover files erased by FORMAT.
SYSTFORM.COM: This program is like the format utility but formats the system tracks on the diskette only.
VERIFY.COM: This utility calculates cyclic redundancy check characters from all sectors and compares them to the CRCCs written on the diskette in the drive queried. If an error exists its location will be displayed, if not the prompt is returned.
DENSITY.COM: A program to determine and display the density of the diskette in the drive queried.
SDIR.COM: This utility displays an alphabetized disk directory when called.
COPY.COM: Often, i t is easier or necessary to copy an entire diskette rather than transfer files one at a time.
The COpy utility is provided for this purpose. Note that COpy will only transfer data between like-density formatted diskettes (single to single or double to do uble) •
There are three forms of COpy, each for a different task.
COpy A (copy All system and data tracks),
COpy S (copy just the System area, tracks 0,1) COpy D (copy just the Data area, tracks 2 - 76)
Prompts are displayed by the program requesting the source disk (the master from which the copy is made) and the destination disk. Use of COpy is illustrated in DISTRI- BUTION DISKETTE DUPLICATION below.
FILES.COM: The directory entries for a disk and the blocks used are indicated by this 'transient. The first three 8- digit groups of numbers are the file name and type; the
fourth indicates the extent in the first two digits and the number of records used in the extent (in hex) in the l a s t two d i g i t s (the middle 4 digits have no significance); and the remainder indicate the specific blocks used. Note that this utility can be invoked on the current disk only.
CPM62.COM: This is not a utility. It is a duplicate of the Micromation CP/M operating system set up for operation in 62K of RAM. It is provided as a convenience in new system generation. Refer to Appendix C for an example of its use.
RAMTEST.COM: This utility was written to check the RAM in Micromation systems. It mayor may not run in non- Micromation syst.ems. Refer to the listing (RAMTEST.ASM) on the distribution diskette to see if it has utility.
4-4 OTHER FILES
DISKDEF.LIB: DISKDEF is used with the Digital Research Macro assemb1·er. It has no utility beyond its use with this program. Refer to the CP/M 2.2 Alteration Guide.
DEBLOCK.LIB: This file is supplied by Digital Research and conains sector blocking and deblocking algorithms. Refer to the CP/M Alteration Guide for a discussion of this feature . - - -
CBIOS.LIB, BIOS.LIB, BOOT.LIB: These files are d istr ibuted by Digital Research as examples of the BIOS and BOOT programs. They are for reference only. To alter the system, use MM2BIOS.ASM and M2BOOT.ASM descr ibed below.
LIST.SUB, STEP.SUB: These files are used with the CP/M SUBMIT utility to change the IOBYTE and step time respectively. See Appendix C-2 for a description of their use.
The remainder of the files on the distribution diskette, with file type ASM, are the source files of the Micromation generated utilities. Many users will find these files immaterial for day to day operation. However, system builders may find these very useful, especially when developing dedicated application packages. Most of the ASM files have corresponding COM files, some don't. Those that don't are discussed below.
C2PROM.ASM: This file contains the code of the DOUBLER PROM at board location D4. It is provided for reference.
As such i t can be used to develop special application packages that require knowledge of and/or access to DOUBLER routines and their locations.
MM2BIOS.ASM: MM2BIOS is the source file of the BIOS portion of CP/M. Micromation has written this section to allow system alteration with a minimum of fuss. Refer to THE MICROMATION BIOS below for a description of the default characteristics.
M2BOOT.ASM: M2BOOT, like the custom BIOS, is another part of the CP/M O/S. Its ro1 e is to 10 ad the system. If y'o u change the size parameter in MM2BIOS, a corresponding change must be made in M2BOOT. The two fi1es,must then be
re-assemb1ed and inserted in the system.
4-5 THE MICROMATIOH BIOS
The BIOS (Basic Input/Output System) portion of CP/M is custom tailored to accommodate the Micromation hardware. In addition, several parts are conditionally assembled to suit the user's application. "Conditionally assembled" means that portions of the program are not included during assembly unless a flag is set true. To reset them to alter the system configuration, see New System Generation below.
The system characteristics are established in BIOS and are as follows. (Your system may have slightly different characteristics if i t was configured for a non-Micromation hardware environment.)
- a system size of 62K
- the serial port on the DOUBLER for console (CON:) device with an appropriate driver - 3 parallel ports on the Multi I/O board
assigned to the line printer (LPT:) option for LST: with a driver routine
for a Centronics type dot matrix printer - the serial port on the Multi I/O Board
assigned to the TTY: option for LST:
with a driver routine for a serial interface printer
The following table summarizes the relationship between logical and physical device assignments as established in BIOS at cold boot.
CON:
=
CRT: ( through the DOUBLER serial port) RDR:=
TTY:PUN:
=
TTY:LST:
=
LPT: (Centronics 703/779 printer through Multi I/O board parallel ports)Although RDR: and PUN: are assigned to TTY:, they are not supported in the BIOS. Attempts to output to PUN: or input from RDR: will not work.
The l i s t device (LST:) is assigned to the line printer (LPT:) option. The BIOS currently contains a driver for a Centronics 703/779 printer to correspond with this assignment. This is a parallel input dot matrix printer connected through the parallel ports on the I/O board.
The next section has twofold significance. First, it presents the procedures for backing up the distribution diskette, for making a double master from the distribution diskette, and, finally, for making work disks for use in the day to day operation of your computer system. Second and equally as important, execution of
these procedures provides hands-on experience in use of the utilities for the operator.
5 CP/M INTER-VERSION COMPATIBILITY
The operating system shipped with the DOUBLER is the latest version of the popular CP/M O/S from Dig ital Research. (As of this writing, the version number is 2.2. This is subject to change as new revisions are distributed.) In the single density recording format, there's complete compatibility between this and previous versions. In double density recording, there is an important difference. This difference will destroy the data stored in a file when transferring i t from a diskette record~d
under an earlier version to one recorded under version 2.2 (or later) or vice versa. Use the following procedure to move files from diskettes recorded in double density by previous versions to double density disks created under the new 2.2 system.
1) Put the old system m~ster in drive A. Use your old FORMAT program to initialize enough disks in drive B to accommodate the files presently on your double density disks.
2) Using the old version of PIP, transfer the program and data files from the double density disks to the newly created single density disks. Do not transfer any utilities (also referred to as transient commands); the ones provided with your new system diskette will replace those from the previous version.
3) Place a single or double density CP/M version 2.2 (or later) disk in drive A and your single density disk created above in drive B. Use PIP from the new version to transfer the program and data files from B to A. Do not use the version of PIP from the earlier revision of CP/M.
Transfer all the files from your double density disks created under a previous CP/M version to the new one in this manner.
Do not use the Micromation COPY utility to make 2.2 duplicates of your 1.4 or earlier double density disks. This will render the files on the 2.2 disk unreadable.
Do not use any utilities from previous versions. Use only the ones prov ided on the d i str ibut ion d i sket teo
SECTION 2
THEORY OF OPERATION
6 INTRODUCTION
The DOUBLER is a byte oriented floppy disk controller. It has an on board PROM that allows for bootstrap s t a r t , and holds primitives that control hardware systems on the board. Features include single and double density disk formats with automatic selection of the format on the disk, an RS-232 serial port with baud rate select, and a variety of control configurations for the S-100 bus.
The disk controller transfers data under program control on a sector by sector basis. In CP/M compatible single density format there are 26 sectors per track with 128 bytes per sector transfered at a data bit rate of 250KHz (IBM 3740 standard). In the double density format there are 52 sectors per track with 128 bytes per sector transfered at a data bit rate of 500KHz.
The intent of this theory of operation is to describe the hardware systems on the DOUBLER. Since there are many references to the schematic diagrams, component parts are referenced by the page number of the schematic followed by the part number. The part numbers on the schematic also refer to the column and row that the package occupies on the board. After the part number, the part type is listed in parentheses. For instance 2IC10C (74LS374) refers to page 2 of the schematic, IC l0C (which is the IC in column 10 at row C), of the type 74LS374.
6-1 DISK SYSTEM OPERATION
When the disk system is to be accessed the intent of the operator is translated by CP/M into a sequence of events. The drive to be used, selection of read or write, and the file to be found, are provided, indirectly, by the operators actions. These parameters are then processed by the operating system to access the appropriate portion of the disk.
Disk I/O is performed by a sequence of calls to the disk access subroutines, and by hardware that performs the ongoing processes of encoding, decoding, and phase lock to the serial data stream.
When a request for disk access is made, the operating system readies the file to be written to the disk or allocates memory space to accept the file read from the disk. The operating system must then select the drive to be accessed, load the read/write head and move i t to the proper track on the disk, phase lock the controller to the serial data stream on the disk, locate the sector to be operated on, perform a read or write record operation, and determine if the transfer is completed. If the transfer is not complete the next record is selected,
located, and written to or read from, until the transfer is completed.
The routines used ·to control the disk drive, and interface to the operating system are in BIOS and the C2-PROM (Appendix B is a
listing of the C2-PROM). The routines in the C2-PROM are an extension of BIOS. They are closest to the DOUBLER hardware, while BIOS holds the more executive functions. A listing of the MICROMATION custom BIOS and C2-PROM can be found in the distribution diskette, and information on the standard model BIOS
is included in the CP/M reference manuals.
The parameters used to access the sector on the disk are held ·in the scratch pad RAM. For example, TRACK, SECTOR, DMA (the address of a memory buffer used for the source or destination of data during transfers), and DENBYTE are registers in the RAM that pertain directly to sector read/write operations. A complete list of these registers is included in the C2-PROM listing.
When a disk is accessed for the first time after being inserted in the drive, i t is logged and tested for density. Testing for density is executed by trying to read the SYNC FIELD HEADER on track 2 in single density. After 30 unsuccessful tries at single density, double density is tested. DENBYTE, in the scratch pad RAM, is set according to test results.
6-2 DISK READ/WRITE
During disk read and write operations the operating system loads the head, steps to the selected track, and tests DENBYTE for the density of the disk. A call to the SYNC subroutine then finds the sync field header (see Appendix A if unfamiliar with the sector format) in the ID FIELD and establishes the synchronization of PLO and the byte sync counter with the moving disk data. Once in sync, the operating system looks for the sector ID MARK. When it is found, the track intended is checked against the track read. If i t is the correct track, a sector by sector search is executed until the selected sector is found.
eRC is checked during these operations to ensure that the disk has been read correctly.
After the proper sector has been found, read or write of the DATA FIELD begins. When a read operation has been requested, the operating system looks for the DATA MARK, then reads the 128 bytes of data in the sector, and finally checks the eRe to confirm the accuracy of the data. When a write operation has been requested, the operating system writes ~ new SYNC FIELD HEADER and a DATA MARK in the data· field, then writes 128 bytes of data followed by the CRee
Read or write operations are a byte by byte transfer of a sector of data to or from the system memory area marked by the disk memory address, DMA, (not to be confused with direct memory access). After a sector has been read, the operating system
takes the information in the memory area marked by DMA and uses i t to build the file being read. The operating system then provides parameters on a new sector to be transfered, and transfers i t , or ends the read operation. After a sector has been written, another sector of data is placed in the memory area marked by DMA, and transfered, or the write operation is ended.
7 THE S-199 BUS INTERFACE
The DOUBLER's S-100 bus interface has three sections; the control bus, the bidirectional data bus (D0-D7), and the address bus (A0- AIS) •
7-1 THE CONTROL BUS
The control bus is used to control data transfers between the processor and memory or peripherals. The DOUBLER uses the following signals:
PDBIN is used by the processor to indicate that a valid address is on the address bus and that i t is reading data on data bus 1 ines D0-D7 from memory or an I/O port.
/PWR is used by the processor to indicate that a valid address is on the address bus and that it is outputting data on data bus lines D0-D7 to memory or an I/O port.
SINP and SOUT are used by the processor to indicate input or output, respectively, to an I/O port. They are similar to the PDBIN and /PWR signals and are active when these signals are in coincidence with /IOREQ. These lines disable the DOUBLER when active.
SINTA indicates that the processor is in an interrupt mode.
The DOUBLER is disabled when this'signal is active.
/PHANTOM disables the RAM that occupies the same memory position as the DOUBLER. It is active whenever the DOUBLER is enabled.
PSYNC is a synchronizing signal used with a 4MHz CPU clock to synchronize wait state requests to the processor machine cycles.
/PRST (reset) is used on the DOUBLER board to generate a power on jump which accesses the jump to BOOT instruction in the resident firmware.
XRDY and PRDY are wait state inputs to the processor. One of these control lines (user option) is used by the DOUBLER floppy disk interface to make the CPU wait, on a byte by byte basis, during data transfers to and from the disk.
7-2 THE DATA BUS
The bidirectional data bus handles data transfers between the DOUBLER and the processor. It is isolated from the on board data bus by a bidirectional tri-state buffer, consisting of lIC10D
(74LS244) and IICIID (8304).
This buffer writes data to the DOUBLER board whenever /PWR is active, and reads data to the bus when PDBIN is active and the board is enabled by the address decoder. When the DOUBLER is not enabled the data bus buffers are in a high impedance state.
7-3 THE ADDRESS BUS
The address bus is used to enable and select registers that comunicate with the disk system on the DOUBLER board, and to access the UART, scratch pad RAM, and the C2-PROM.
8 ADDRESS BUS DECODING
Decoding of the high order address bits takes place in the address decoder PROM lIC9C (74S287). The low order bits are connected directly to the devices addressed or to the read/write control.
8-1 THE ADDRESS DECODER PROM
The address decoder generates the /RAM, I/O, PROM, and BD signals from address lines A9-A15. Decoding of these lines takes place in the bipolar PROM, IIC9C (74S287). Note that address inputs to lIC9C do not correspond to address bus lines. The A3 input to lIC9C is set by the NOR of control bus signals SINP, SOUT, and SINTA. If any of these lines are active the decoder PROM output lines, and the board, are not enabled. BD is active whenever /RAM, I/O, or PROM are active. BD is used as the board enable, and inverted, it drives the /PHANTOM line.
The DOUBLER occupies the memory space from F800H to FFFFH. This area is divided into three sections as follows.
8-2 THE C2-PROM
C2-PROM
Scratch pad RAM I/O
F800H - FBFFH FC00H - FDFFH FE00H - FFFFH
The C2-PROM, 6IC9D(2708), is enabled by the PDBIN and PROM enable signals, accessed by address lines A0-A9, and based at address F800H. It holds the bootstrap loader and routines that control the DOUBLER. Refer to the C2PROM.ASM listing in Appendix B.
8~3 THE SCRATCH PAD RAM
The 64 byte scratch pad RAM, 6IC9A (4036), is accessed by address lines A0-A5. It is selected by the /RAM signal from the address decoder. RAM output enable and R/W are controlled by the /WR signal. This RAM is assigned the dedicated registers and the stack used by the routines in C2-PROM and BIOS.
8-4 READ AND WRITE CONTROL
The read/write control generates strobes that operate the read, write, control, and status latches on the DOUBLER's internal data bus. Its inputs are address lines A0-A2, /WR, /PDBIN, and I/O.
This circuit consists of two, eight wide data distributors, lIC7D and lIC6D (74LSl38). Both of these are enabled by the I/O signal from the address decoder PROM. lIC6D and lIC7D are also enabled by /PDBIN and /WR, respectively, /PDBIN enables the read control;
/WR enables the write control. Low active strobes generated by the read/write control memory map are listed in firmware as follows.
ADDRESS FE00H FE0lH FE02H FE04H FE05H FE06H FE07H FE0AH
/WR WRCONT WRCLK WRUART WRMRKCRC WRMRK
WRDATA WRCRC
/PDBIN RDSTAT RDUART RDMRKRC RDMARK
RDDATA SYNCPORT UARTSTAT
These strobes and their corresponding latches perform the following functions.
WRCONT loads the drive control latch, 5IC10A (74S374), which operates the drive control lines.
RDSTAT reads the drive status latch, 5ICIIA (74LS224), which contains the drive status lines.
WRCLK writes the clock pattern to the sync mark latch, 2IC12D (74LS273). This value is then compared with the clock pattern from the SYNC FIELD HEADER to synchronize with the moving disk data.
WRUART and RDUART write and read to the UART, 6IC13D (8251), used for the RS-232 serial interface.
WRMRK is a strobe that writes an ID or a DATA MARK to the disk (depending on the status of the MRKA signal).
RDMRK is a strobe that holds the processor until a MARK is read (or the timeout triggers) in order to synchronize the byte sync counter. It is also used to clear the head load counter.
WRMRKCRC and RDMRKCRC are strobes that perform the same functions as WRMRK and RDMRK, respectively, and also preset the cyclic redundancy check circuit.
WRDATA and RDDATA these strobes act ivate the DISKWR and /DISK READ signals respectively. Addressing these ports transfers data to or from the disk on a byte by byte basis.
WRCRC is a strobe used to gate the cyclic redundancy check"
character into the serial data stream.
SYNCPORT is a strobe used in the synchronization of the byte s yn c co un t e r •
UARTSTAT accesses the control and status latches in the UART.
Address line A2 is used to enable the DISKWR and /DISKREAD signals. All strobes listed above in the address range of FE04H - FE07H also transfer data to or from the disk when active.
8-5 THE UART
The UART, 6IC13D (8251), is based at FE02H, and selected by the /RDUART and /WRUART signals from the READ/WRITE CONTROL. Address line A3 is connected to the UART C/D input, which accesses its control and status latch, based at FE0AH.
9 DISK DRIVE INTERFACE
The operating system controls and monitors the drives via the drive control latch (WRCONT), which operates the dr ive control input lines, and the drive status latch (RDSTAT), which contains the drive status outputs. These latches and their pin connection to the disk drive list as follows:
BIT PIN WRCONT PIN RDSTAT D0 36 /STEP 22 /RDY
Dl 34 /DIR 10 /SEEK DONE
D2 SD/DD 18 /HEAD
D3 32 /DRIVE D 20 /INDEX D4 30 /DRIVE C 24 /SECTO~t
D5 28 /DRIVE B 44 /WRITE PRT D6 26 /DRIVE A 42 /TRACK 00 D7 12 /RESTORE CRCSTAT
CRCSTAT and SD/DD are listed in the latches but do not connect to the drives. The other signal pin connections to the drives are:
PIN FUNCTION 8 /ABOVE 43
38 /DISK WRITE DATA 40 /WRITE GATE
46 /RAW DATA
9-1 THE PHASE LOCK OSCILLATOR
The heart of the floppy disk system is the phase lock oscillator, PLO, which generates signals used to synchronize to the moving disk data. Phase lock is the process of synchronizing an oscillator to an external signal. In order to work, control of
the output frequency of the oscillator and a system to detect the frequency differences between the external signal and the oscillator must exist. The final part of the phase lock system is a feedback loop that allows the detector to control the o sc ill a to r •
In the DOUBLER, control of the PLO output frequency is achieved by digitally dividing the signal from an oscillator with a
frequency twenty times higher than the frequency to be generated.
The divider (a preset counter string) can be set to divide by any integer in the domain of 1 to 45.
Detection of frequency difference is executed by latching the divider status when a transition of the external signal (raw disk data) occurs.
The feedback loop is completed by a PROM that is coded to use the divider status as an input to output a preset value that will correct the difference in frequency.
The DOUBLER's PLO consists of a 20 MHz crystal oscillator, 4 Yl and 4IC4A (74S04), which drives a presetable counter string, 4IC2A (74LS163) and 4IC3A (74LS161-A). The nominal count for double density is 20D, which yields a 1 MHz clock rate which is approximately equal to the frequency of the serial stream from the disk. The nominal count for single density is 40D which yields 500KHz. Notice that these values are twice the data transfer rate. This is necessary to accommodate the interleaved data and clock bits.
Preset values are provided for the counter string by one of two PROMs, the Rl, 4ICIB (74S471), for read and the WA, 4IC2B (74S471), for write. The counters are continuosly being incremented by the 20MHz clock. The log ic condi tioned raw data stream is used as a clock input to the latch, 4ICIA (74LS174).
Data inputs to this latch are connected to the stage outputs of the counter string. When a pulse comes down the raw data stream
the current count of the counter string is stored in the latch.
Outputs of this latch connect to the address inputs of the Rl PROM. If there is an error in timing between the disk data stream and the PLO, the preset value of the counter string is changed by the contents of the PROM to correct the timing error.
Since data on the disk is frequency modulated, changes in timing caused by modulation must be ignored, so the Rl PROM is coded to compensate only the larger errors in timing. If there is no incoming pulse during the current PLO count cycle, (when reading a zero data bit for example), the latch is cleared. If the incoming pulse is on time, the latch stores zero. Either of these conditions set the counter string to the nominal value, a~d
PLO remains synchronous to the disk data stream.
PLO is the clock input of the byte sync counter, and is also used to shift disk data into the shift register, 2ICllB and 2ICllC (74LSl64), used for conversion of raw disk data to eight bit parallel bytes. PLO is locked to the signal from the disk any tim e in for mat ion is rea d fro m th e dis k. ( W r i teo pe rat ion s involve a read of the ID field to verify the track and locate the sector to be written to.) Since the frequency to be locked is known, phase lock can be achieved in a few cycles.
During write operations, after the sector has been located, PLO becomes a frequency synthesizer and is set to the nominal frequency. Data is brought from the data bus to the disk write data latch, 2ICl0B (74LSl65), and is shifted serially out by the PLO signal. This serial stream goes through the CRC, multiplexer, encoder, and precompensator, and then to the disk drive.
9-2 THE BYTE SYNC COUNTER
The byte sync counter, 3IC4B (74LSl6l), provides signals used to separate clock bits from data bits and define the beginning and end of bytes in moving disk data. Outputs from this counter are also sent to the multiplexer, 3IC3B (74LSl57), to insert clock bits into the disk write data and provide information for write precompensation (see section 9-5).
The byte sync counter is clocked by the /DPLO signal.
signal is PLO delayed by 512JNs which is one cycle of the oscillator. /DPLO is used so that circuits using PLO can before action is taken on their outputs.
This 212JMHz settle
The byte sync counter is set, if not in sync, when SYNCPLO is addressed by the operating system. The counter is set so that C/D is high with respect to data bits in the moving disk data, EOC is high during data bit 7 and EOW is high during clock bit 121.
The SYNCMARK signal is connected to the "B" load input of the counter. If SYNCPLO is addressed and the counter is not in sync the high on the "B" load input is loaded. This steps the counter toward byte synchronization.
Detection of SYNCM~RK starts in the shift register, 2ICllC and 2ICllB (74LSl64), which is used to separate clock bits from data bits, and convert moving disk data into parallel bytes.
Alternating stages of this shift register are connected to the disk read data latch, 2IC1~C (74LS374J, and the SYNCMARK comparator, 2ICl2B and 2ICl2C (74LS266). The SYNCMARK comparator sees the clock bits from the shift register and codes loaded by the operating system into the sync mark latch, 2ICl2D (74LS273).
When the codes in the sync mark latch and the shift register match, the SYNCMARK signal goes low. This sets EOC from the byte sync counter, 3IC4B (74LS16l), and loads the multiplexed data pattern, from the SYNC FIELD HEADER, into the disk read data latch, 2IC1~C (74LS374). The operating system reads this latch and, if the proper code is found, verifies sync and continues the read or write sector operation.
9-3 WAIT STATES (XRDY or PRDY)
Data recovery from the disk is slower than the cycle time of the
cpu.
Consequently the XRDY or PRDY lines are held low to hold the processor in a wait state and allow the current byte of the disk read or write operation to be transfered. The byte sync counter output, EOC, marks the end of. a byte. EOC is used to l i f t the wait state and transfer a complete data byte from the DOUBLER to the data bus, or from the data bus to the DOUBLER.If for ~()'1tle reason the DOUBLER cannot complete the byte transfer, a timer, lICl3A· (4~4~), is used to prevent loss of dynamic RAM data. It lifts the wait state before the refresh timing limits of dynamic RAM are exceeded.
Wait states must also be generated when a 4MHz processor clock is used. PSYNC and BD (board enable) coincidences are detected in an AND gate lICSD (74LS00). When coincidence is detected XRDY and PRDY become active, generating one wait state per board access.
'This is needed to allow adequate access time for the C2-PROM. A jumper labeled "WAIT" can be found at location D-4 on the DOUBLER. It must be installed to operate at 4MHz.
9-4 THE CYCLIC REDUNDANCY CHECK
The cycl ic redundancy check, CRC, is an on going process carr ied on by the CRC IC, 3IC8B (8Sg6). During write operations a complex logic creates a unique code from the data sent to the sector, called the cyclic redundancy check character (CRCC), which is appended to the sector. During disk read operations the CRCC is read from the disk and compared with the character calculated from the data just read. If an error condition is found, the operating system attempts to read again. If sub- sequent retries fail, the operating system displays an error message.
9-5 ENCODING AND WRITE PRECOMPENSATION
The double density recording format pushes the recording medium to the limit. When two transitions of magnetic polarity are written adjacent to each other, they interact, causing a shift in timing. This shift makes the data stream unreadable. The solution is to write adjacent pulses shifted, so that their interaction yields the correct position in time along the disk serial data stream. This corrective shift of timing, prior to write, is called write precompensation. In the DOUBLER, compensation in wr i te tim ing is achieved by mov ing the posi tion of clock bits with respect to data bits. The mechanism for doing this is in the PLO. The PLO is a digitally controlled frequency synthesizer. During read, frequency control is used to achieve synchronization with the moving data stream on the disk. During write, clock pulses are offset in time by changing the count of the counter string, 4IC2A and 4IC3A (74LSl61A), on a bit by bit basis.
During write, control of the PLO counter string is executed by the WA PROM, 4IC2B (74S471). The address inputs to this PROM rep res en t a po r t ion 0 f the s e ria 1 d a t a s t rea m mix e d wit h c 10 c k.
The data outputs of the PROM are connected to the preset inputs of the counter string. Coding in the PROM presets the counter str i ng to prov ide wr i te precompensat ion.
WA PROM output 07 is the serial data stream sent to the disk during write.
encoding disk the WA PROM.
densi ty. So always set to frequency.
Coding in the PROM also holds the algorithms for data. Both single and double density codes are in Write precompensation is not used in single for single density write the counter string is the nominal count, which yields a 500KHz output
19 THE RS-232 SERIAL INTERFACE
The terminal interface consists of an RS-232 serial interface designed around the UART, 6IC13D (8251), on the DOUBLER. The UART clock is derived from system clock by counters, 6IC14D (74LS161), and 6ICl4A (4024). Baud rate is selectable via a jumper from the outputs of the counters. There is a provision for use of the on board 20MHz clock to generate the 2MHz UART clock via 6IC3C (74LS90 not provided), if the host system has a different clock frequency.
The following is a list of the RS-232 connections:
J2-l J2-2 J2-3 J2-5 J2-6 J2-7 J2-9
TxD GND /RTS /DSR /DTR
leTS
/RxD
transmitter data ground
request to send data set ready
data terminal ready clear to send data receiver data
To connect a video display terminal, signal groundv TxD, and /RxD are all that need be connected. The other signals are for handshake arrangements not usually necessary for terminals.
11 POWER ON JUMP
When power is first applied to the computer, or the reset button is pushed, a reset (/PRST) pulse is generated activating the power on jump circuit on the DOUBLER which generates a /POJ signal. With this signal active the C2~PR~M is enabled, and the JMP COLDBOOT instruction at address F8~~H in the PROM is executed. Since the high order address bits are decoded by the address decoder, F8~~H appears to be ~~~~H when /POJ is active.
COLDBOOT reads tracks "~" and "1" (the system tracks) of the diskette in drive llA" into memory locations ~~~~H-~~7FH, and then executes the transferred code by per;,forming a jump to ~~~~H, to load the system into memory. .~ .
12 POWER SUPPLY
The DOUBLER runs on the S-l~~ bus supply line voltage. On board regulation produces +5v, -5v, +12v, and -12v. The +5 volt line can draw more than an ampere, while the other lines draw less than 5~ milli amperes.
Ceramic disk capacitors are distributed along the power rails, in accordance with ~ood digital logic design, to reduce noise.
